# Electrical Measurements & Units Test Questions - 7

1)   During load test on 3 phase induction motor, the readings of the two wattmeters are -5.5 kW and +12.5 kW respectively. If the line voltage is 420 V then the line current will be

a. 38.91 A
b. 41.02 A
c. 42.10 A
d. 43.94 A
 Answer  Explanation  Related Ques ANSWER: 43.94 A Explanation: No explanation is available for this question!

2)   The two wattmeters used for the measurement of power input read 50 kW each. What will be the readings of the two wattmeter if the power factor is changed to 0.8 leading keeping the total input power same?

a. 28.35W, 71.65W
b. 31.25W, 73.71W
c. 33.33W, 73.33W
d. 38.35W, 75.5W
 Answer  Explanation  Related Ques ANSWER: 28.35W, 71.65W Explanation: No explanation is available for this question!

3)   Ballistic galvanometer are principally used for the measurement of

a. Current
b. Voltage
c. Power
d. Electric charges
 Answer  Explanation  Related Ques ANSWER: Electric charges Explanation: No explanation is available for this question!

4)   Vibration galvanometer are generally used

a. For measuring electric charges
b. As null-point detectors in ac bridges
c. As null-point detectors in dc bridges
d. For measuring power
 Answer  Explanation  Related Ques ANSWER: As null-point detectors in ac bridges Explanation: No explanation is available for this question!

5)   The meter of a vibrating reed frequency meter depends for its indications on the

a. Electrical resonance of thin flat steel reeds
b. Mechanical resonance of thin flat steel reeds
c. Mechanical resonance of thick flat steel reeds
d. Electrical resonance of thick flat steel reeds
 Answer  Explanation  Related Ques ANSWER: Mechanical resonance of thin flat steel reeds Explanation: No explanation is available for this question!

6)   The electrodynamic frequency meters have

a. Linear scale and their readings does not depends on voltage
b. Linear scale and their readings depends on voltage
c. Non linear scale and their readings does not depends on voltage
d. Non linear scale and their readings depends on voltage
 Answer  Explanation  Related Ques ANSWER: Linear scale and their readings does not depends on voltage Explanation: No explanation is available for this question!

7)   A moving iron frequency meter consists of

a. Two inductive circuits connected in parallel
b. One inductive and one non inductive circuit connected in parallel
c. Two non inductive circuits connected in parallel
d. One inductive and one non inductive circuit connected in series
 Answer  Explanation  Related Ques ANSWER: One inductive and one non inductive circuit connected in parallel Explanation: No explanation is available for this question!

8)   If the frequency of electrodynamic power factor meter is doubled then its reading will become

a. Twice of the original reading
b. Half of the original reading
c. Four times of the original reading
d. Remains unaffected
 Answer  Explanation  Related Ques ANSWER: Remains unaffected Explanation: No explanation is available for this question!

9)   Moving iron power factor meter are suitable for 3 phase balanced circuits. It consists of

a. One control spring
b. Two control spring
c. Three control spring
d. No control spring
 Answer  Explanation  Related Ques ANSWER: No control spring Explanation: No explanation is available for this question!

10)   In Nalder-Lipman moving iron power factor meter, the magnetic field produced

a. Rotates in clockwise direction
b. Rotates in anticlockwise direction
c. Rotates in both clockwise and anticlockwise direction alternately
d. No rotating magnetic field is produced
 Answer  Explanation  Related Ques ANSWER: Rotates in clockwise direction Explanation: No explanation is available for this question!

11)   A series reactance coil is used in Weston frequency meter. This coil is used to

a. Suppress harmonics present in the current flowing through the meter
b. Minimizes the waveform errors
c. Both (a) and (b)
d. None of these
 Answer  Explanation  Related Ques ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!

12)   The coils of rotating type phase sequence indicator are mounted at

a. 60 degree apart in space
b. 90 degree apart in space
c. 120 degree apart in space
d. 180 degree apart in space
 Answer  Explanation  Related Ques ANSWER: 120 degree apart in space Explanation: No explanation is available for this question!

13)   The instrument which works only with dc is

a. Electrolytic motor
b. Mercury motor
c. Induction motor
d. Both (a) and (b)
 Answer  Explanation  Related Ques ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!

14)   The electrolytic energy meters are essentially

a. A true watt-hour meter
b. An ampere hour meter
c. Either watt-hour or ampere hour meter
d. Neither watt-hour nor ampere hour meter
 Answer  Explanation  Related Ques ANSWER: An ampere hour meter Explanation: No explanation is available for this question!

15)   An electrolytic ampere hour meter can be converted into watt-hour meter by

a. Multiplying them by the voltage of the circuits in which it is used
b. Multiplying them by the current of the circuits in which it is used
c. Multiplying them by the power of the circuits in which it is used
d. Cannot be converted
 Answer  Explanation  Related Ques ANSWER: Multiplying them by the voltage of the circuits in which it is used Explanation: No explanation is available for this question!

16)   Commutator type meters can be used for

a. AC supply
b. DC supply
c. Both AC and DC supply
d. None of these
 Answer  Explanation  Related Ques ANSWER: Both AC and DC supply Explanation: No explanation is available for this question!

17)   In case of motor meters, the speed of rotation is

a. Directly proportional to the current in case of ampere hour meter and to power in case of watt-hour meter
b. Directly proportional to the current in case of ampere hour meter and inversely proportional to the power in case of watt-hour meter
c. Inversely proportional to the current in case of ampere hour meter and directly proportional to the power in case of watt-hour meter
d. Inversely proportional to the current in case of ampere hour meter and to power in case of watt-hour meter
 Answer  Explanation  Related Ques ANSWER: Directly proportional to the current in case of ampere hour meter and to power in case of watt-hour meter Explanation: No explanation is available for this question!

18)   In motor meters, the speed control of the rotating system is done by using

a. Permanent magnet
b. Train of gear wheels and dials
c. Pinion
d. All of these
 Answer  Explanation  Related Ques ANSWER: Permanent magnet Explanation: No explanation is available for this question!

19)   Commutator motor meters are

a. Ampere hour meter
b. True watt-hour meter
c. Either ampere hour meter or true watt-hour meter
d. None of these
 Answer  Explanation  Related Ques ANSWER: Either ampere hour meter or true watt-hour meter Explanation: No explanation is available for this question!

20)   The induction type single-phase watt-hour meters uses

a. Control spring
b. Pointer
c. Brake magnet and spindle
d. All of these
 Answer  Explanation  Related Ques ANSWER: Brake magnet and spindle Explanation: No explanation is available for this question!

21)   In induction watt-hour meter, due to shunt magnet the torque is not zero power factor. It can be compensated by using

b. Power factor compensator
c. Both (a) and (b)
d. None of these
 Answer  Explanation  Related Ques ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!

22)   For friction compensation in an induction watt-hour meter is done by making

a. The ratio of the shunt magnet flux and series magnet flux large with the help of two shading bands
b. The ratio of the series magnet flux and shunt magnet flux large with the help of two shading bands
c. The ratio of the shunt magnet flux and series magnet flux large with the help of three shading bands
d. The ratio of the series magnet flux and shunt magnet flux large with the help of three shading bands
 Answer  Explanation  Related Ques ANSWER: The ratio of the shunt magnet flux and series magnet flux large with the help of two shading bands Explanation: No explanation is available for this question!

23)   Current transformers and potential transformers are used to increase the ranges of

a. AC ammeter and AC voltmeter respectively
b. AC ammeter and DC voltmeter respectively
c. DC ammeter and DC voltmeter respectively
d. DC ammeter and AC voltmeter respectively
 Answer  Explanation  Related Ques ANSWER: AC ammeter and AC voltmeter respectively Explanation: No explanation is available for this question!

24)   For the measurement of energy and power it is essential to know

a. Only the transformation ratio
b. Phase angle between the primary and secondary currents
c. Both (a) and (b)
d. None of these
 Answer  Explanation  Related Ques ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!

25)   The transformer ratio of the transformer depends upon the

a. Exciting current
b. Secondary current
c. Power factor of secondary circuit
d. All of these
 Answer  Explanation  Related Ques ANSWER: All of these Explanation: No explanation is available for this question!

26)   Primary current in a current transformer is determined by

a. The load on the system
b. The load on its own secondary
c. The load on its own primary
d. All of these
 Answer  Explanation  Related Ques ANSWER: The load on the system Explanation: No explanation is available for this question!

27)   The potential transformers are used to measure large voltage using

a. High range voltmeter
b. Low range voltmeter
c. High range ammeter
d. Low range ammeter
 Answer  Explanation  Related Ques ANSWER: Low range voltmeter Explanation: No explanation is available for this question!

28)   If an instrument transformer is used to extend the ranges of AC instrument, then its reading will depend on

a. R
b. L
c. C
d. None of these
 Answer  Explanation  Related Ques ANSWER: None of these Explanation: No explanation is available for this question!

29)   The nominal ratio for a current transformer is given by

a. rated primary winding current / rated secondary winding current
b. no. of turns in the primary winding / no. of turns in the secondary winding
c. no. of turns in the secondary winding / no. of turns in the primary winding
d. rated secondary winding current / rated primary winding current
 Answer  Explanation  Related Ques ANSWER: rated primary winding current / rated secondary winding current Explanation: No explanation is available for this question!

30)   The resistances of potential transformer winding is minimized by using

a. Thick conductors and small length of turns
b. Thin conductors and small length of turns
c. Thin conductors and large length of turns
d. Thick conductors and large length of turns
 Answer  Explanation  Related Ques ANSWER: Thick conductors and small length of turns Explanation: No explanation is available for this question!

31)   In potential transformer, with increase in frequency the phase angle

a. Increases
b. Decreases
c. Remains same
d. None of these
 Answer  Explanation  Related Ques ANSWER: Increases Explanation: No explanation is available for this question!

32)   Under normal operating condition, the excitation current of current transformer and potential transformer

a. Both varies over a wide range
b. Varies over a wide range, remains constant
c. Remains constant, varies over a wide range
d. Both remains constant
 Answer  Explanation  Related Ques ANSWER: Varies over a wide range, remains constant Explanation: No explanation is available for this question!

33)   CRO gives the visual representation of time varying signals. The display of the signal is

a. One dimensional
b. Two dimensional
c. Three dimensional
d. Four dimensional
 Answer  Explanation  Related Ques ANSWER: Two dimensional Explanation: No explanation is available for this question!

34)   Principally CRO is a

a. Ammeter
b. Voltmeter
c. Wattmeter
d. Watt-hour meter
 Answer  Explanation  Related Ques ANSWER: Voltmeter Explanation: No explanation is available for this question!

35)   The sweep generator of a CRO is used to produce

a. Sinusoidal voltage for the horizontal deflection of electron beam
b. Saw tooth voltage for the vertical deflection of electron beam
c. Sinusoidal voltage for the vertical deflection of electron beam
d. Saw tooth voltage for the horizontal deflection of electron beam
 Answer  Explanation  Related Ques ANSWER: Saw tooth voltage for the horizontal deflection of electron beam Explanation: No explanation is available for this question!

36)   Which part is called as heart of CRO?

a. CRT
b. Sweep generator
c. Trigger circuit
d. Amplifier
 Answer  Explanation  Related Ques ANSWER: CRT Explanation: No explanation is available for this question!

37)   The light emitted by the zinc silicate coated fluorescent screen of cathode ray tube is usually of

a. Green colour
b. Yellow colour
c. Blue colour
d. White colour
 Answer  Explanation  Related Ques ANSWER: Green colour Explanation: No explanation is available for this question!

38)   If the bombardment of electrons cease i.e. when the signal becomes zero then the light emitted by the screen will

a. Disappear immediately
b. Persist for some time then it will disappear
c. Will not disappear at all
d. None of these
 Answer  Explanation  Related Ques ANSWER: Persist for some time then it will disappear Explanation: No explanation is available for this question!

39)   In terms of the division on screen, the voltage of the waveform in CRO is

a. Average voltage
b. RMS voltage
c. Peak to peak voltage
d. Maximum voltage
 Answer  Explanation  Related Ques ANSWER: Peak to peak voltage Explanation: No explanation is available for this question!

40)   The Lissajous patterns help in the measurement of

a. Phase difference between two sine wave
b. Frequency of one waveform if the frequency of other waveform is known
c. Both (a) and (b)
d. None of these
 Answer  Explanation  Related Ques ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!